The objective of this study is to characterize the surface of blood pumps, total artificial hearts and left ventricular assist pumps, after in vivo experiments with the devices implanted in calves. Studies involve mapping the thickness of pseudoneointima formed on the various components and characterizing the structure of the deposited layer by scanning and transmission electron microscopy as well as standard histological techniques. BIBLIOGRAPHIC REFERENCE: Nose, Y., Kiraly, R.J., Picha, G.: Surface characteristics of cardiac prostheses in vivo. J. Biomed. Mater. Res. Sym., No. 8, p. 85, 1977.